Materials World Network: Interfacial Phenomena in Superconducting Heterostructures

本研究的目的是合成、表征和研究外延异质结构中与界面现象相关的实验和理论性质，这些异质结构由复杂的氧化物超导体（铜酸盐）、铁磁体（锰酸盐）和氧化物超导体组成，并结合氧化栅绝缘体的场效应结构。这项工作结合了西班牙研究人员（马德里康普顿斯大学的Jacobo Santamaria）利用相对简单的高压氧溅射技术制造氧化物外延膜的技术，以及美国明尼苏达大学（Allen Goldman）和佐治亚理工学院（Carlos Sa de Melo）的研究人员及其在阿贡国家实验室（Suzanne ter Velthuis）和橡树山国家实验室（Maria Varela）的合作者的理论和实验能力。这项工作的统一概念是利用氧化铁磁体的自旋和场效应门的感应电荷来研究高温超导薄膜的基态和激发态。主要研究方向有两个：(1)复合氧化物超导/铁磁异质结构中的自旋注入及其相关现象；(2)复合氧化物超导纳米膜中的电荷效应和量子有序。研究了自旋注入对准粒子和铜膜凝聚态的影响，以及Andreev反射和磁邻近效应对铜膜自旋弛豫时间和长度的影响。本文还探讨了在铁磁氧化物中诱导外来配对态的可能性，以及利用场效应将赝隙相中“掺杂不足”的铜调至超导态的可能性。后一项工作的目标是研究使用场效应掺杂来确定赝隙和超导相之间边界的零温度端点是否为连接两个不同超导基态的量子临界点。用于解决这些问题的实验工具包括电子隧道和电传输，以及与橡树岭和阿贡国家实验室的合作者，电子显微镜和中子散射。所使用的理论工具包括许多平行和补充实验研究的身体技术。这一国际性的努力使得来自美国和西班牙的学生和博士后同事之间有了强有力的互动，这拓宽了全球科学界年轻科学家的经验。该奖项与国际科学与工程办公室共同资助。

The objectives of this research are to synthesize, characterize, and study experimentally and theoretically properties associated with interfacial phenomena in epitaxial heterostructures consisting of complex oxide superconductors (cuprates), and ferromagnets (manganites) and oxide superconductors incorporated into field effectstructures with oxide gate insulators. This effort combines the techniques developed by the Spanish investigator (Jacobo Santamaria, Universidad Complutense, Madrid) for the fabrication of epitaxial films of oxides using relatively simple high-pressure oxygen sputtering techniques, with the theoretical and experimental capabilities of the US investigators at Minnesota (Allen Goldman) and Georgia Tech (Carlos Sa de Melo) and their collaborators at Argonne (Suzanne ter Velthuis) and Oak Ridge National Laboratories (Maria Varela). The unifying concepts of this effort are the use of spin from an oxide ferromagnet and induced charge from a field effect gate to study the ground state and excited states of high temperature superconducting films.There are two main research themes: (1) Spin injection and related phenomena in complex oxide superconducting/ferromagnetic heterostructures and (2) charge effects and quantum order in complex oxide superconducting nano- films. The effects of spin injection on the quasiparticles and the condensate of cuprate films and the roles of Andreev reflections and the magnetic proximity effect on the spin relaxation time and length in cuprate films are examined. The possibilities of inducing exotic pairing states in ferromagnetic oxides and using the field effect to tune the properties of an "under doped" cuprate in the pseudogap phase into the superconducting state are also explored. A goal of the latter effort is to investigate the use of field effect doping to determine whether the zero-temperature end point of the boundary between the pseudogap and the superconducting phases is a quantum critical point connecting two different superconducting ground states. The experimental tools used to address these issues include electron tunneling and electrical transport, and with collaborators at Oak Ridge and Argonne National Laboratories, electron microscopy and neutron scattering. The theoretical tools used involve many body techniques that parallel and complement the experimental investigations. This international effort allows for strong interaction of students and postdoctoral associates from the US and Spain, which broadens the experience of young scientists in the global scientific community.This award is co-funded with the Office of International Science and Engineering.